1. Technical Field
The present invention relates to an exposure head that exposes an exposure surface or an image carrier having a curvature by converging light emitted from light emitting elements onto the exposure surface or the image carrier. The invention also relates to an image forming apparatus including the exposure head.
2. Related Art
Exposure heads that expose an exposure surface by converging light emitted from light emitting elements onto the exposure surface using an optical system have been known. Exposure heads have been generally used to expose an exposure surface having a curvature, such as a peripheral surface of a photosensitive drum (image carrier). JP-A-2008-036937 discloses an exposure head (a “line head” in the Publication) including a plurality of optical systems disposed at different positions with respect to a direction in which the exposure surface has a curvature (a “sub-scanning direction” in the Publication). In this exposure head, each the optical systems converges a light emitted from a light emitting element at a position facing the optical system in the optical axis direction.
However, in the aforementioned exposure head, the optical systems converge the light at different positions with respect to the direction in which the exposure surface has a curvature. Therefore, the position at which one optical system converges a light on the exposure surface and the position at which another optical system converges a light on the exposure surface may be displaced from each other with respect to the optical axis direction. As a result, the sizes of converged light formed on the exposure surface by the optical systems may become different from each other. Such a difference between the sizes of the converged light formed by the optical systems may cause a defective and uneven exposure.